Not all narratives have to have a plot. While it's very highly recommended it's not one hundred percent mandatory, and this is how the literary canon gets things like Finnegans Wake, where things like "characters" and "story" emerge not from an ordinary reading, but from decades of analysis and argument by English professors, from swerve of shore and bend of bay and so on. Still, very few of us are of the caliber of James Joyce, able to produce something that is regarded as one of those weird classics of literature and which is nevertheless absolutely opaque. Beyond that, there are successful slice-of-life works, which don't necessarily have a plot so much as a series of events. No plot in real life, after all.
On the whole, though, plots are important when you're creating a story no matter what mechanism you're using it to create it - words, art, music, and so on. What's equally important is the motivation for the characters to move through the plot. Sure, on occasion it's understandable and believable for a character to be caught up in events, but a whole story of that is unsatisfying. The key to a good story is allowing a disentangled character to follow the plot for her own reasons. The necessity for choice is a fundamental part of a good plot, as it puts control of the situation into the hands of the character you're following; particularly when you're talking about a protagonist, you want to be in control of the situation. What you don't want to be is a puppet of outside events.
It's a lot easier to encounter this problem in the modern generation of video games, many of which are essentially interactive stories. It's still a new medium, only a few decades old, and so it's understandable that creators are still coming to grips with the opportunities and pitfalls inherent in it. While this doesn't apply universally, when it comes to games that are story-driven and advertise themselves as specifically role-playing games, I think the issue of motivation should be a key one to consider.
Take, for example, Fallout 3. Released in 2008, it was the long-awaited follow-up to the two original games of the late 1990s about survival, discovery, and justice in post-apocalyptic California. Ten years of technical refinement makes it stand apart substantially from its predecessors; while the original games used an isometric, overhead view with a turn-based battle system in which the echoes of rolling dice were never far away, Fallout 3 thrusts the player into the game with a default first-person perspective and a limited third-person viewpoint that owes far more to first-person shooters than to its RPG heritage. Granted, this is a popular mechanism today, and using that kind of viewpoint does not diminish the quality of a game's story - what it does do, for me at least, is increase my investment in the story. Ordering around the Vault Dweller or the Chosen One from somewhere high in the sky is one thing, but when you're looking through the Lone Wanderer's eyes, her story gains that immediacy as well.
If only the creators of the game had actually made a story worth that feeling.
The biggest problem that I saw in Fallout 3's plot was that most of the world that Bethesda created for it was wasted. When you boil it down not only is it simple, but it's extremely easy to end up on a treadmill straight to the ending without even realizing you're on it. The game's plot begins with you looking for your father and ends with you saving the Wasteland, and while there's a wealth of additional content scattered across the ruins of D.C. there is very little reason, in terms of plot and motivation, why your character would ever find it. The whole "find your father" plot is actually very straightforward - in the first town there's a guy who tells you he went somewhere else, and when you arrive there there's a guy who tells you he went to another place, and once you arrive at that place you get sent to where your father is. There's no misdirection, no uncertainty, no discovery - the only difficult bits are ensuring you have enough money or a sufficiently silver tongue to get the people with the proper knowledge to give it to you.
Where's the in-story reason to wander around the Wasteland? It's not like you have to assemble the fragments of a puzzle leading to where your dad is. There isn't one. It's a game of connect the dots, but following up on the non-plot content is basically your character saying "all right, I know where to go to find my dad so that things will be comfortable and familiar and the way they were before," and instead deciding to traipse around the blasted Wasteland with two hundred pounds of weapons and armor, getting poisoned by radscorpions and shot at by super mutants, because... because.
The first time I played through Fallout 3, I obediently followed the story because I figured "hey, Bethesda went to the trouble of building this huge-ass open world, it's not like they're going to waste ninety percent of it." Then I realized I was on the last mission of the main campaign. I'm thankful I bought the Game of the Year addition, which includes the extra downloadable content that was released after the original game, because I would have been pissed as hell if the game had ended the way it did originally.
I know that not everyone will see things the way I do - but role-playing video games are a new mode of storytelling, with a great capacity to tell stories. I don't like it when that capacity isn't used to its utmost.